Article Figures & Data

Figures

Differential expression of mesothelin by human lung cancer cells. Immunoreactive mesothelin was measured by flow cytometry using the antimesothelin monoclonal antibody K1. Nonspecific immunoreactivity of the cells to a FITC-conjugated secondary goat antimouse antibody was used as negative control. Samples of the NCI-H226 human NSCLC cells consisted of 99.5% mesothelin-positive cells (bottom left panel). The PC14PE6 human adenocarcinoma cells were negative (0%) for mesothelin (bottom right panel). These are representative profiles from one of two measurements.

Immunofluorescence staining of mesothelin in human lung target cells. Tumor cells were first reacted with the primary antimesothelin monoclonal antibody K1 at a 1:500 dilution and then incubated with a 1:200 dilution of secondary goat antimouse antibody conjugated to Texas Red. The expression of mesothelin was identified by red fluorescence. The specific immunofluorescence for mesothelin was higher in the NCI-H226 human NSCLC cells (A) than in PC14PE6 human adenocarcinoma cells (B).

In vitro dose response of the NCI-H226 human NSCLC cells and PC14PE6 human adenocarcinoma cells to immunotoxins. Cells from exponentially growing cultures were seeded into 96-well tissue culture plates and treated with the indicated concentrations of immunotoxins. Four days later, the antiproliferative effects of the immunotoxins were determined by the MTT assay. The IC50s were calculated. Mesothelin-expressing NCI-H226 cells were more sensitive to the cytotoxic effects of the antimesothelin immunotoxin SS1(dsFv)-PE38 than the mesothelin-negative PC14PE6 cells. Neither cell line responded to the anti-Tac(dsFv)-PE38 control immunotoxin (IC50 > 100 ng/ml). This is one representative experiment of three.

Tables

Nude mice were injected i.v. with NCI-H226 (2.5 × 105) or PC14PE6 (1 × 106) cells on day 0 and treated with i.v. administration of PBS, anti-Tac(dsFv)-PE38 control immunotoxin (10 μg/0.2 ml/mouse), or SS1(dsFv)-PE38 antimesothelin immunotoxin (10 μg/0.2 ml/mouse) on days 7, 9, and 11. Mice injected with NCI-H226 cells were killed on day 51. Mice injected with PC14PE6 cells were killed on day 45. The results shown are representative from one of three independent experiments.